The Four Noble Truths were the first teachings given by the Buddha, and form the very basis of Buddhist philosophy because it explains how to gain freedom from the influence of disturbing emotions and karma.

Below is a short teaching given by Ringu Tulku, explaining the Four Noble Truths:

A way to get a deeper understanding of the Four Noble Truths is to study the sixteen aspects, which are four aspects for all of the four noble truths. This is a way to enrich ones understanding of the Four Noble Truths and to help one understand why and how liberation is actually possible.

Each of the sixteen aspects are meant to counteract a misunderstanding of the Four Noble Truths. Here is a link from a teaching by Alex Berzin, explaining the 16 misunderstandings that are being counteracted.

And here is a helpful link explaining the actual sixteen aspects of the Four Noble Truths, also from a teaching by Alex Berzin